The method was developed by Willard Libby in the late 1940s and soon became a standard tool for archaeologists.Libby received the Nobel Prize in Chemistry for his work in 1960.
Research has been ongoing since the 1960s to determine what the proportion of in the atmosphere has been over the past fifty thousand years.
The resulting data, in the form of a calibration curve, is now used to convert a given measurement of radiocarbon in a sample into an estimate of the sample's calendar age.
By contrast, methane created from petroleum showed no radiocarbon activity because of its age.
The results were summarized in a paper in Science in 1947, in which the authors commented that their results implied it would be possible to date materials containing carbon of organic origin.
Atmospheric nuclear weapon tests almost doubled the concentration of concentrations in the neighbourhood of large cities are lower than the atmospheric average.